Fig. 1. Flow chart of adaptive wavelet threshold algorithm

Fig. 2. Spectral detection hardware platform

Fig. 3. Copper spectral signal collected by ATP2000 spectrometer. (a) Background light intensity; (b) reference light intensity; (c) sample light intensity; (d) absorbance curve

Fig. 4. Spectral signal and calibration curve of copper and cobalt. (a) Spectral signal of copper; (b) spectral signal of cobalt; (c) linear correction curve of copper; (d) linear correction curve of cobalt

Fig. 5. Spectral signal and calibration curve of copper and cobalt after denoising. (a) Spectral signal of copper; (b) spectral signal of cobalt; (c) linear correction curve of copper; (d) linear correction curve of cobalt

Fig. 6. Ratio curve of dual wavelength intensity. (a) Ratio curve at the wavelengths of 445 nm and 525 nm; (b) ratio curve at the wavelengths of 456 nm and 492 nm

Fig. 7. Spectral signal calibration curve